1. Field of the Invention
The present invention relates to a radiation detecting element and a radiographic imaging device. The present invention particularly relates to a radiation detecting element with plural pixels arrayed in a matrix, in which charges generated due to irradiation of radiation are accumulated, and the amount of accumulated charges are detected as image information, and to a radiographic imaging device that uses the radiation detecting element for imaging a radiographic image.
2. Description of the Related Art
In recent years, radiographic imaging devices using a radiation detecting element such as a flat panel detector (FPD) that includes a radiation-sensitive layer placed on a thin-film transistor (TFT) active matrix substrate and can convert radiation such as X-rays directly into digital data, have been put to practical use. FPDs have advantages in that, compared to conventional imaging plates, images can be checked instantaneously and moving images can also be checked, and the spread of FPDs is rapidly progressing.
Various types are proposed for such radiation detecting element. There are, for example, direct-conversion-type radiographic imaging devices that convert radiation directly to charge in a semiconductor layer, and accumulate the charge. There are also indirect-conversion-type radiographic imaging devices that first convert radiation into light with a scintillator, such as CsI:Tl, GOS (Gd2O2S:Tb) or the like, then convert the converted light into charge in a semiconductor layer and accumulate the charge.
In radiation detecting elements, charges are generated by dark current or the like, even when the pixels are not being irradiated by radiation, and the charges are accumulated in the pixels. Accordingly, in the radiographic imaging devices using the radiation detecting elements, during standby, a reset operation that extracts and removes the charges that have been accumulated in the pixels are repeatedly performed. Further, in the radiographic imaging devices using the radiation detecting elements, when imaging, the reset operation are stopped, and the charges are accumulated during the irradiation period in which the pixels are irradiated by radiation. Furthermore, after the end of the irradiation period, the radiographic imaging devices using the radiation detecting elements perform read-out of the charges that have been accumulated in the pixels of the radiation detecting element.
As technologies that synchronize the timing of irradiation of radiation and the timing of the start of charge accumulation by the radiation detecting element, Japanese Patent Application Laid-Open (JP-A) No. 2002-181942 and JP-A No. 2007-151761, discloses a sensor capable of detecting radiation placed separately outside an imaging region of the radiation detecting element. In these technologies, accumulation of the charges is started by the radiation detecting element when radiation has been detected by the sensor.
Here, in radiographic imaging, the region where the radiation is irradiated is set as narrowly as possible, in order to prevent unnecessary exposure of examinees and radiologic technologists to radiation. That is, the region irradiated with radiation is set such that only the portion to be imaged is irradiated by radiation.
Accordingly, in the technologies described in JP-A No. 2002-181942 and JP-A No. 2007-151761, since the region irradiated with radiation has been narrowly set, there are cases where irradiation of radiation cannot be detected with the sensor.